Two-dimensional
perovskite compounds, (RNH
3
)
2
PbX
4
, have attracted much attention as quantum confinement
materials. To achieve suitable orientation and exciton properties
for optical applications, carboxy groups were introduced into the
ammonium cations of two-dimensional perovskite compounds, which formed
dimer structures based on the hydrogen bonding by the carboxy moieties.
This structural organization allowed control of the layer orientation
for favorable solar cells and thermal stability of the perovskites,
while maintaining quantum confinement effects.
Push-coating
is a simple process that can be employed for extremely
low-cost polymer electronic device production. Here, we demonstrate
its application to the fabrication of poly(2,7-carbazole-alt-dithienylbenzothiadiazole) (PCDTBT):[6,6]-phenyl-C71-butyric
acid methyl ester (PC71BM) active layers processed in air,
yielding similar photovoltaic performances as thermally annealed spin-coated
thin films when used in inverted polymer solar cells (PSCs). During
push-coating, the polydimethylsiloxane layer temporarily traps the
deposition solvent, resulting in simultaneous film formation and solvent
annealing effect. This removes the necessity for a postdeposition
thermal annealing step which is required for spin-coated PSCs to produce
high photovoltaic performances. Optimized PSC active layers are produced
with a push-coating time of 5 min at room temperature with 20 times
less hazardous solvent and 40 times less active material than spin-coating.
Annealed spin-coated active layers and active layers push-coated for
5 min both produce average power conversion efficiencies (PCEs) of
5.77%, while those push-coated for a shorter time of 1 min yield a
slightly lower value of 5.59%. We demonstrate that, despite differences
in their donor:acceptor vertical concentration gradients, unencapsulated
PCDTBT:PC71BM active layers push-coated for 1 min produce
PSCs with similar operational stability and upscaling capacity as
thermally annealed spin-coated ones. As fast device fabrication can
be achieved with short-time push-coating, we further demonstrate the
potential of this deposition technique by manufacturing push-coated
PSC-based semitransparent photovoltaic devices with a PCE of 4.23%,
relatively neutral colors and an average visible transparency of 40.2%.
Our work thus confirms that push-coating is not limited to the widely
employed poly(3-hexylthiophene-2,5-diyl) but can also be used with
low band gap copolymers and opens the path to low-cost and eco-friendly,
yet efficient and stable PSCs.
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